ass (1)
beast of burden, O.E. assa (Old Northumbrian assal, assald), prob. from O.Celt. *as(s)in "donkey," which (with Ger. esel, Goth. asilus, Lith. asilas, O.C.S. osl) is ultimately from L. asinus, probably of Middle Eastern origin (cf. Sumerian ansu). Since ancient Gk. times, in fables and parables, the animal typifies clumsiness and stupidity (hence asshead, 1550, etc.). To make an ass of oneself is from 1590. Asses' Bridge (c.1780), from L. Pons Asinorum, is fifth proposition of first book of Euclid's "Elements."